change the […] to Read More link in the exerpt?

Have a look at the functions.php file in the Twenty Eleven theme. That theme does exactly what you want, so you should be able to re-use that approach/code in your own theme.

Yes, or you can find this code in your index.php file (and the other file in your theme’s template PHP files :
<?php the_content(); ?>
…and change it to this:
<?php the_content('Read More...'); ?>

thanks but I don’t think that will work,

I recently added this to my loop-standard.php page to display exerpts:

<?php if ( is_category() ) { // if this is the category archive
     the_excerpt( '<a href="%permalink">Read more</a>' ); // return the excerpt
} else {
     the_content( 'Continue reading', 'wap8lang' ); // return the content
} ?>

I am using the SANS theme
https://themeforest.net/item/sans-a-responsive-portfolio-wordpress-theme/2390498

I’m sorry but as you are using a commercial theme, you need to seek support from the theme’s vendors. We do not support commercial themes here.